1. Field of the Invention
The present invention relates to a projector apparatus, a control program for the projector apparatus and a light source controlling method for the projector apparatus. The projector apparatus uses light sources which emit light beams of different colors to project an image.
2. Description of the Related Art
Conventionally, a projector apparatus having a halogen lamp light source has been used in general. In recent years, a projector apparatus which employs, as light sources, three LEDs respectively emitting red, green and blue light beams has been proposed to downsize the apparatus and to make the apparatus portable. However, the projector apparatus which uses the three LEDs cannot project an image with a higher luminance. This is because the LEDs emit light beams by turns, and in each moment, only one of the red, green and blue LEDs is emitting a light beam. In addition, luminance of an LED is lower than that of a halogen lamp.
Jpn. Pat, Appln KOKAI Publication No. 2004-317558 discloses a projector which can project an image with a higher luminance. According to the projector, when a light beam of one color is emitted from an LED, the other LEDs are driven by low power to emit light beams. For example, while an LED is emitting a red light beam, the other LEDs are driven by low power and emit green and blue light beams. Thus, an image can be projected with a higher luminance.
However, an LED has characteristics that a color of the emitted light beam varies with a value of the drive current when the driving current is lower than the rated current for the LED. That is, when an LED is driven by low drive current to emit a light beam, the color of the light beam differs from the original emission color of the LED.
Therefore, when the red LED emits the red light beam and the green and blue LEDS are driven by the low power to emit the green and blue light beams, a total emission color from the projector differs from a combination of a large amount of red, a little amount of green and a little blue. The total emission color includes colors which are varied from green and blue due to the low power driving in addition to red and presents an unexpected color.
Moreover, an LED deteriorates as the LED is used longer (as emitting time becomes longer). Therefore, with the deterioration, the luminance of the LED is decreased and chromaticity may also be varied. Thus, the above projector, in which while one LED (red, for example) is emitting a light beam, the other LEDs (green and blue) are also driven, deteriorates more quickly than a projector in which only one of the LEDs emits a light beam at a time. As a result, the total emission color of the projector may include colors which are varied from green and blue due to the deterioration in addition to red and presents an unexpected color.
Therefore, according to Jpn. Pat. Appln. KOKAI Publication No. 2004-317558, although an image can be projected with a higher luminance, chromaticity adjustment for the projected image is impossible.